New fuel assemblies to be used in a nuclear power plant (fresh fuel assemblies; hereinafter, referred to simply as fuel assemblies) are manufactured in a fuel production plant before transported to the nuclear power plant as contained in transportation containers which have shielding, sealing, and other functions. If fuel assemblies under transportation are subjected to vibrations or an impact during transportation, the fuel assemblies may be deformed. The fuel assemblies may also be damaged by friction with metal contacting parts. In order not to impair product integrity and reliability, fuel assemblies therefore need to be securely fixed to the transportation containers.
In a conventional transportation container, fuel assemblies are placed sideways in the container body, and then the fuel assemblies are fastened by attaching fastening members such as a clamping frame at predetermined intervals over the entire length of the fuel assemblies (for example, see Patent Literature 1). Since fuel assemblies have a length of approximately 4 m, the fastening operation takes a lot of time and effort. The operation of loading fuel assemblies into a transportation container has thus been quite time-consuming.
Patent Literature 2 describes a transportation container which has been known as an example of a transportation container for facilitated fastening operation. The transportation container described in Patent Literature 2 includes a basket for containing a plurality of fuel assemblies inside the transportation container. The basket includes a plurality of rectangular pipes that accommodate fuel assemblies. Fastening devices are arranged along the longitudinal directions of two of the four side walls that constitute each rectangular pipe. The fastening devices each include: a plurality of clamp plates that are arranged at predetermined intervals along the longitudinal direction of the rectangular pipe and configured to be movable back and forth in the rectangular pipe; a plurality of drive units that are linked to the respective clamp plates and drive the clamp plates back and forth; and a rotating shaft that connects the drive units and simultaneously drives the drive units for rotation. An operator can operate an operation part at the end of the rotating shaft in an opening of the basket, whereby the rotation is transmitted to the plurality of drive units through the rotating shaft and the plurality of clamp plates are simultaneously driven back and forth. Seats for holding the lower ends of fuel assemblies are installed at the lower ends of the rectangular pipes that constitute the basket. The seats have a recessed shape conforming to the tapered lower end of a fuel assembly.
To load fuel assemblies into the foregoing transportation container, the transportation container is initially arranged upright. Fuel assemblies are vertically hung down and inserted into the rectangular pipes of the basket. Here, the lower ends of the fuel assemblies are guided by the recesses in the seats arranged at the bottoms of the rectangular pipes and thereby supported by the seats. Subsequently, the clamp plates of the foregoing fastening devices are driven so that the plurality of clamp plates press and fasten the fuel assemblies to the wall surfaces of the rectangular pipes. This completes the operation of loading fuel assemblies. According to the transportation container of Patent Literature 2, the operation of fastening fuel assemblies can be performed more easily than with the transportation container of Patent Literature 1. It is therefore possible to reduce the time needed for the operation of loading fuel assemblies into a transportation container.